MnOOH nanoparticles integrated nitrogen doped porous nanosheet-like carbon network as a non-noble catalyst for electro-oxidation of sodium borohydride

Abstract

Nitrogen doped carbon-supported with various ratio of electro-active manganite nanoparticles (MnO–NPCs) as a facile, low-cost, and non-noble electrocatalyst is synthesized for electro-oxidation of borohydride. Transmission electron micrographs show the size of MnO nanoparticles in NPC is about 3.8 ± 0.2 nm with a definite lattice parameter and randomly distributed into the entire nanosheet-like porous carbon network. Survey X-ray photoelectron spectrum (XPS) of MnO–NPCs sample reveals the presence of Mn element; and Mn–O–Mn and Mn–O–H peaks from O 1s, indicating the effective insertion of MnO nanoparticles onto the NPC surface. Electrochemically transformed MnOOH–NPCs are further explored as effective catalysts toward the electro-oxidation of borohydride in 1.0 M alkaline NaOH solution. Among the catalysts with different ratios, MnOOH–NPC-2 displays higher catalytic performance (~19.9 mA ⋅ cm−2) with low-onset polarization potential (−0.65 V) towards borohydride electro-oxidation. The obtained results are mainly owing to (i) the unique nanosheet-like structure of nitrogen doped carbon network access large amount of MnOOH nanoparticles (without any aggregation) through their numerous porous-structure with high-specific surface area (821 m2 g−1), (ii), the presence of intrinsic synergetic activity between porous carbon nanosheets and MnOOH nanoparticles, and (iii) the effective interaction of Mn2+ ions with OH− ions to form Mn(OH)2, which mediates improved catalytic activity of borohydride electro-oxidation.